Recovery of oil and aluminum from oil shale



3,516,787 RECOVERY OF OIL AND ALUMINUM FROM OIL SHALE Robert A. Van Nordstrand, Tulsa, Okla., assignor to Sluclair Research, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Aug. 10, 1966, Ser. No. 571,649 Int. Cl. C01f 7/06, 7/08, 7/14 US. Cl. 23-143 15 Claims ABSTRACT OF THE DISCLOSURE A process for separating oil and aluminum values from oil shale containing kerogens, sodium aluminum carbonate hydroxide, quartz and dolomite by retorting the shale at about 500 to 1200 F. to separate the oil, leaching the resulting spent shale with an alkaline solution at a temperature of up to about 220 F. to dissolve the aluminum values from the shale without substantial precipitation of SiO and recovering the aluminum values as hydrous alumina from the alkaline solution.

The present invention relates to the recovery of oil and aluminum values from oil shales. More particularly, this invention is concerned with the treatment of oil shales containing sodium aluminum carbonates such as dawsonite, and large quantities of silica in order to recover the kerogens and aluminum from the oil shales.

It is, of course, well known that certain sedimentary rocks, commonly referred to as oil shale, upon heating, yield appreciable quantities of relatively crude oil as well as gaseous hydrocarbons. This oil may be refined into valuable products such as gasoline, diesel oil, jet fuel, and fuel oil. Likewise, valuable by-products such as tar acids and waxes are recoverable from the crude shale oil. Extensive deposits of oil shale are found in this country, particularly in the so-called Green River shale formation located in the States of Colorado, Utah, and Wyoming. Important oil shale deposits are likewise found in other parts of the world. With diminishing world reserves, there has been considerable interest in developing a commercially feasible process, suitable for application on a large scale, for retorting (i.e., destructive distilling) oil shale to recover its potential yield of crude oil; however, to date the retorting of oil shales has not been extensively practiced on a commercial scale.

Recently, however, there have become of interest oil shales which have substantial amounts of aluminum-com taining minerals such as dawsonite, i.e., sodium aluminum carbonate hydroxide, which, if recoverable, would increase the economical value of the oil shale. This invention is then directed to the combined recovery of the oil, i.e., by retorting, and the aluminum values from such oil shales to increase the economical potential of these oil shales. Oil shales with which this invention is concerned are found in, for example, Rio Blanco County, Colo. The shales contain about 5 to 40%, particularly about to 30%, kerogens, i.e., hydrocarbons which form the recoverable oil, about 5 to 30%, particularly about 10 to dawsonite, and about 10 to 40%, particularly 20 to quartz, or SiO in some form. Nahcolite also is present in pockets and dolomite makes up the essential remainder of the shale and may comprise about 10 to particularly 20 to 30% thereof.

In general, the process of this invention for the recovery of oil and aluminum values comprises first retorting the shale to recover the oil and then alkali leaching the hot retorted or spent shale to recover the aluminum as sodium aluminate, ultimately as aluminum hydroxide which can be calcined to alumina, a preferred nited Patent Of 3,516,787 Patented June 23, 1970 raw material for aluminum reduction plants. In the first or retorting step, the oil shales are generally crushed, e.g., to a particle size of about A to mm. diameter, preheated and then transferred to a retorting zone where the particles are pyrolyzed to remove the kerogens as a fog or mist and vapors which are subsequently condensed to form an oil.

In one of the retorting methods presently receiving commercial consideration for the recovery of oil from oil-bearing material, oil shale is retorted in such a manner as to maintain a stationary zone of combustion near the top of an oil shale layer and at the same time fresh shale is moved upwardly into this zone of combustion and the products of combustion are drawn downward, countercurrently to the upward moving fresh shale, so as to preheat the latter and at the same time to drive off the mineral oils and also to effect cooling and/or condensation of vaporized oil. In another retorting method, the shale is passed downwardly countercurrently to hot gases so as to separate the oil from the oil-bearing solid material. The details of the retorting process are well known to those skilled in the art, although it is a part of this invention to remove and recover the oil from the shale.

Retorting not only is desirable in this invention to recover the kerogens, but also to convert the shale to a form from which the aluminum values are readily recoverable. Without retorting, the aluminum is difficult to recover from the oil shale since the kerogen makes the aluminum more or less inaccessible, whereas, upon retorting, the shale becomes porous and friable. Furthermore, the decomposition products of dawsonite ar soluble in alkali and recoverable by leaching. Upon heating dawsonite at a temperature of at least about 500 F., for example, the crystalline dawsonite decomposes and becomes amorphous. If heated at about 900 F., cooled and then exposed to air, sodium carbonate and bayerite crystallize out of the amorphous dawsonite. At temperatures of about 1300 F. the dawsonite is converted to crystalline sodium aluminate. The aluminum is, however, readily recoverable by alkali leaching from these various forms. Additionally, retorting decomposes the dolomite in the shale to produce CO calcite and MgO. The MgO ties up part of the SiO to permit higher recovery of the aluminum values by leaching. Otherwise, this SiO can, during retorting or leaching, react with the aluminum to form sodium aluminum silicate from which aluminum recovery is very difiicult and uneconomical.

Retorting temperatures are generally from about 500 to 1200 F., or higher, e.g., 1700 F. preferably about 800 to 1000 F., with the upper temperature being that at which coking or cracking of the recovered oil vapors is a significant problem. Essentially all of the oil is recovered in the range of from about 500 to 1000 F, or 1200 F. With some oil shales, additional heating after retorting may improve aluminum recovery and in all cases retorting is carried out for a sufficient time to convert the dawsonite to a recoverable form. If additional heating is desirable, it may be conducted at temperatures of from about 1000 to 2400 F. for a time after removal of the kergons sufficient to improve aluminum recovery, e.g., up to several hours, preferably about ten minutes to 2 or 4 hours. Whether or not recovery is increased by additional heating may depend upon the particular composition of the shale and each shale may be tested to determine this point.

The shale, after retorting, and additional heating if desired, is leached with a strong alkali solution, e.g., sodium hydroxide, under mild conditions to dissolve the aluminum compound. The leaching conditions include a pH sufiicient to dissolve the aluminum component of the shale, generally a pH above about 10, preferably above 11, and a temperature and time sufficient to dissolve the aluminum component but low enough to avoid dissolving much SiO In general, leaching temperatures of from about room temperature to about 220 F., preferably about 150 to 212 F., are suitable. The temperature should remain below about 220 F. to avoid substantial reaction with SiO since with higher leaching temperatures more SiO is dissolved by the alkali and the SiO,, will re-precipitate with sodium and aluminum as a sodium aluminum silicate from which recovery of the aluminum is quite difficult. Short leaching is desirable to reduce the overall time of the process. Times of about or minutes up to several, e.g., about 2 or more hours, preferably about 5 minutes to 1 hour, can be used, if desired, depending upon the temperatures and pH of the leaching solution, and about to 30 minutes has been found to be particularly suitable for leaching. The alkali solution may contain about 1 to 10 weight percent of sodium hydroxide and is used in a suflicient amount, e.g., above about twice the weight of the solid being treated, to give a fiuid slurry So that the solution will thoroughly leach the retorted shale. From about 10 to 25, or 50, milliliters of alkali solution per 5 grams of solid has been found to be a suitable amount of leaching solution when the solution contains from about 2.5 to 10 wt. percent free sodium hydroxide.

Following leaching, the alkali solution which contains dissolved aluminum is separated from the undissolved solids, e.g., dolomite, quartz, calcite, etc., by filtration or other means. The solution is then cooled and reduced in alkalinity, either by diluting with water or by adding carbon dioxide, to precipitate a hydrous alumina such as gibbsite or bayerite. This hydrous alumina can then be separated from the alkaline mother liquor, washed, and calcined to alumina according to known pr0c dures. The alkaline mother liquor can be adjusted to proper alkalinity and concentration by treating with unslaked lime to precipitate out the carbonate ions and by distilling off some of the Water, and then used to leach additional hot retorted oil shales.

The following examples serve to illustrate the invention.

EXAMPLE I An oil shale from Section 21, Township 1S.98W., Rio Blanco County, Colo., taken over the depth interval 2186' to 2189' was crushed to a A; to inch size. In addition to about 30% kerogens, this shale contains about dawsonite [NaAlCO (OI-I) with the remainder being primarily quartz (SiO and dolomite (CaMg(CO Twenty samples of 80 gm. each were separated. Each sample was placed in an oil shale assay retort constructed so that both the oil and water produced from each sample is recovered and measured. The retort operates with limited access of air, so the pyrolysis of the shale is carried out in the effective absence of oxygen. Pyrolysis of this sample was carried out for 2 hours at 900 F. Each of the 20 portions produced about the same amount of oil, the average being 13.9 cc. for the 80 gm. sample, corresponding to 41.7 gallons of oil per ton of shale. The weight loss of the shale is estimated at The retort was opened while the sample was still hot, about 500 F., and the retorted oil shale was then cooled in air. The retorted oil shale was a black, porous, friable substance. A small portion of this retorted sample was crushed and analyzed by X-ray diffraction. The dawsonite was no longer present in its original crystal form and there was no crystalline compound which could be identified by X-ray diffraction as the product of the dawsonite decomposition. The quartz appears to be pr sent in unchanged amount. The dolomite was partially lost. The expected amount of calcite was observed in the retorted shale. The dawsonite was apparently decomposed to a sodium aluminate (NaAIO A portion of the retorted sample was thentreated by a leaching operation to obtain alumina. The leaching solution consisted of sodium hydroxide and distilled water,

specifically, 50 grams of NaOH per liter of solution. A portion of the retorted shale described above was pulverized, and 5 grams were placed in a 250 ml. Pyrex beaker. Thirty-nine ml. of the leaching solution was added. The mixture was heated to about 180 F. and maintained at this temperature for 15 minutes, with frequent stirring. The mixture was diluted with water and filtered. The filtrate was acidified with hydrochloric acid and heated (driving off carbon dioxide and hydrogen sulfide). The solution was then made slightly alkaline with ammonium hydroxide to precipitate aluminum hydroxide. The latter was filtered off, ignited to A1 0 and weighed. The five gram sample of retorted oil shale produced 0.2283 gram alumina, or a 4.57% recovery. This value when corrected for the 25% weight loss on retorting gives a value of 3.4% alumina based on the raw shale or 68 pounds alumina per ton of raw shale.

EXAMPLE II Table I illustrates the oil and alumina yield obtained from a second group of 20 samples from a second oil shale obtained in the vicinity of the first shale and having essentially the same composition. After retorting at 900 F. for 2 hours, the twenty (3-gram) samples were leached according to the procedure described in Example I using three-fifths of the amount of leaching solution. The alumina yield from samples obtained at depths of 2050 ft. to 2530 ft. average 4.1% alumina based on the retorted shale which is about 3.1% based on raw shale or 62 pounds alumina per ton of raw shale. The alumina yield is clearly related to the dawsonite content, shown in Table I, as measured by X-ray diffraction analysis of the individual oil shale samples.

TABLE I Alumina Dawsouite produced Oil yield content (rel- (percent on (previous ative by X Sample (foot Oil p1'0 retorted assay) (galray diffracdepth) duced shale) lens/ton) tion Yes 0. 11 14 0.00 Yes 0. 17 9 0.00 Yes 0. 59 10 0.00 Yes 0.06 28 0.00 Yes 0. 03 26 0. 00 Yes 0. 00 13 0. 00 Yes 0. 00 31 0. 00 Yes 2. 07 11 0. 27 Yes 0.23 11 0.03 Yes 4. 94 17 0. 61 Yes 2.05 24 0. 47 Yes 2. 41 11 0.25 Yes 5. 50 41 1.00 Yes 5. 22 25 0. 49 Yes 6.62 55 0.80 Yes 3. 38 33 0. Yes 3. 4O 48 0. 63 2,530 Yes 3. 62 33 0. 2,588 Yes 0. 15 9 0. 00 2,650 Yes 0. 03 45 0. 00

EXAMPLE III Retorting-leaching studies were made on an oil shale core obtained approximately five miles from the first samples and at the interval 2044-2053 ft. The core was very high in nahcolite (NaHCO low in oil and low in dawsonite, i.e., about 10% dawsonite and 15% kerogens together with substantial quantities of quartz and dolomite. The core was retorted at 900 F. for 2 hours. This retorted shale was then pulverized and subdivided for individual tests. Portions were heated an additional hour at selected temperatures to simulate sequences of temperatures in a gas retort wherein the oil is driven off first, then the temperature was raised and in some cases the coke and sulfide were removed by a surface oxidation wave.

A second temperature study was made on another core taken at the same location over the depth interval 2252 54 ft. This sample had about 30% kerogens, about 20% clawsonite and little or no nahcolite with the remainder being essentially dolomite and quartz.

TABLE II Alumina pro- Sample (It. duced (pourgis/ on Retort temp. depth) Oil produced (1 hr. exposure) (gallons/ton) 1,700 F 1,900 F. 2 hrs.) 1 F EXAMPLE IV TABLE III Percent A1203 recovery 15 min.

NaOH (wt. percent) 30 min.

TABLE IV A120; recovery (wt. percent) 23 ml. soln/ gm.

soli

12 ml. soln/B gm. solid N aOH (wt. percent) TABLE V A1203 recovery (wt. percent) 180 F. 140 F. 100 F.

It is claimed:

1. A process for the separation of oil and aluminum values from oil shale containing the same comprising retorting an oil shale having a composition including about 5 to 40% kerogens, about 5 to 30% sodium aluminum carbonate hydroxide, about 15 to 40% quartz and 10 to 40% dolomite at a temperature of from about 500 to 1200 F. and for a time sufficient to drive off the kerogens and to render the sodium aluminum carbonate hydroxide amorphous, leaching resulting spent the shale with an alkaline solution at a temperature of up to about 220 F. to dissolve the aluminum values from the shale without substantial precipitation of SiO separating, cooling and reducing the alkalinity of the solution containing the aluminum values to precipitate hydrous alumina and recovering the hydrous alumina.

2. The process of claim 1 wherein the spent retorted shale resulting from the retorting step is heated after removal of the kerogens and prior to leaching at a temperature and for a time sufiicient to improve the recovery of said aluminum values, said temperature being from about 1000 to 2400 F.

3. The process of claim 2 wherein the last-mentioned time is up to about four hours.

4. The process of claim 1 wherein the pH of the leaching solution is above 10.

5. The process of claim 1 wherein the pH of the leaching solution is above 11.

6. The process of claim 5 wherein the leaching temperature is about 150 to 212 F.

7. The process of claim 6 wherein the leaching time is between about 5 minutes and 2 hours.

8. The process of claim 7 wherein the alkaline leaching solution contacts the retorted shale while the shale is still hot as a result of said retorting.

9. The process of claim 8 wherein the retorted shale is at a temperature of about 212 F. when contacted by said alkaline solution.

10. The process of claim 7 wherein the leaching time is less than 1 hour.

11. The process of claim 7 wherein said reduction of alkalinity comprises treating the alkaline solution with carbon dioxide.

12. The process of claim 7 wherein said reduction of alkalinity comprises diluting the alkaline solution with water.

13. The process of claim 12 wherein the alkaline solution is cooled to a temperature below about 100 F.

14. The process of claim 11 in which the alkaline solution is cooled to a temperature of below about 100 F. before the addition of carbon dioxide.

15. The process of claim 11 in which the alkaline solution is cooled to a temperature of below about 100 F. after the addition of carbon dioxide.

References Cited UNITED STATES PATENTS 1,891,609 12/1932 Scheidt 2352 2,141,132 12/1938 Folger 2352 2,468,654 4/1949 Brundell et al. 21 2,592,468 4/1952 Rex et al. 106-100 2,904,445 9/1959 Sellers et al. 106-100 2,947,606 8/1960 Holderreed et al. 23143 2,973,244 2/1961 Spence 2352 3,135,618 6/1964 Friese 208-11 PATRICK P. GAtRVIN, Primary Examiner P. E. KONOPKA, Assistant Examiner US. Cl. X.R. 

